The advantageous performance of hybrid organic–inorganic perovskite halide semiconductors in optoelectronic applications motivates studies of their fundamental crystal chemistry. In particular, recent studies have sought to understand how dipolar, dynamic, and organic cations such as methylammonium (CH₃NH₃⁺) and formamidinium (CH(NH₂)₂⁺) affect physical properties such as light absorption and charge transport. To probe the influence of organic–inorganic coupling on charge transport, we prepared the series of vacancy-ordered double perovskite derivatives A₂SnI₆, where A = Cs⁺, CH₃NH₃⁺, and CH(NH₂)₂⁺. Despite nearly identical cubic structures by powder X-ray diffraction, replacement of Cs⁺ with CH₃NH₃⁺ or CH(NH₂)₂⁺ reduces conductivity through a reduction in both carrier concentration and carrier mobility. We attribute the trends in electronic behavior to anharmonic lattice dynamics from the formation of hydrogen bonds that yield coupled organic–inorganic dynamics. This anharmonicity manifests as asymmetry of the interoctahedral I–I pair correlations in the X-ray pair distribution function of the hybrid compounds, which can be modeled by large atomistic ensembles with random rotations of rigid [SnI₆] octahedral units. The presence of soft, anharmonic lattice dynamics holds implications for electron–phonon interactions, as supported by calculation of electron–phonon coupling strength that indicates the formation of more tightly bound polarons and reduced electron mobilities with increasing cation size. By exploiting the relatively decoupled nature of the octahedral units in these defect-ordered perovskite variants, we interrogated the impact of organic–inorganic coupling and lattice anharmonicity on the charge transport behavior of hybrid perovskite halide semiconductors.

中文翻译：

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混合空缺订购的双钙钛矿中的非谐波和八面体倾斜

混合有机-无机钙钛矿卤化物半导体在光电应用中的优越性能促使人们对其基本晶体化学进行研究。特别地，最近的研究试图理解偶极，动态和有机阳离子，例如甲基铵（CH ₃ NH ₃ ⁺）和甲ami（CH（NH ₂）₂ ⁺）如何影响物理性质，例如光吸收和电荷传输。为了探究有机-无机耦合对电荷传输的影响，我们制备了一系列空位有序的双钙钛矿衍生物A ₂ SnI ₆，其中A = Cs ⁺，CH ₃NH ₃ ⁺和CH（NH ₂）₂ ⁺。尽管几乎相同的立方结构通过粉末X射线衍射，更换Cs的⁺用CH ₃ NH ₃ ⁺或CH（NH ₂）₂ ⁺通过降低载流子浓度和载流子迁移率来降低电导率。我们将电子行为的趋势归因于氢键形成的非谐晶格动力学，该氢键产生有机-无机动力学耦合。这种非谐性表现为杂化化合物X射线对分布函数中八面体I–I对相关的不对称性，这可以通过刚性[SnI _6]的随机旋转的大原子团来建模。]八面体单位。软非谐晶格动力学的存在对电子-声子相互作用具有影响，这通过计算电子-声子耦合强度来支持，该强度表明形成更紧密结合的极化子，并且随着阳离子尺寸的增加，电子迁移率降低。通过利用这些缺陷排序的钙钛矿变体中八面体单元的相对解耦性质，我们研究了有机-无机耦合和晶格非谐性对混合钙钛矿卤化物半导体的电荷传输行为的影响。